1. Field of the Invention
This invention relates to pumps and, particularly to positive displacement pumps for high pressure applications, and to pump heads for such pumps.
2. Description of Related Art
High pressure pumps are used in water blasting systems to blast away scale, deck paint, rust or contaminants with a high pressure stream of water. Such systems have applications in oil refineries, chemical plants, oil field operations, offshore operations, and marine industries. Pumps capable of producing pressures up to 50,000 psi have been used with both water systems and water-and-sand-injection systems. These pressurizing pumps are designed to deliver high pressure water or other fluid and are usually based on positive displacement pistons or rubber/diaphragm/hydraulic systems. They may discharge the water or fluid into a common manifold to which are connected flexible hoses or rigid tubing which in turn have nozzles or lances connected to them. The pumps can be mobile or permanently mounted.
U.S. Pat. No. 3,870,439 (co-owned with this invention) discloses a pump head for a high pressure pump which is designed specifically for high pressure cleaning service. It has been made with stainless steel parts which afford corrosion resistance and relatively long service life and it has been provided with a modular design which permits quick and easy maintenance. The pump head can be overhauled in less than two hours and the suction and discharge valves are contained in a clamped valve seat that is easily removable for maintenance. The pump head also has self-adjusting plunger packing contained inside a removable cartridge for quick removal, inspections or replacement Peak pressures developed by the pump plunger, particularly during cavitation, are transmitted to the valve seat unit and to the pump plunger packing rather than to the much more expensive pump manifold.
Despite the advantages and success of the pump head of U.S. Pat. No. 3,870,439, failures have occurred while a pump with such a head operated above pressures of 12,500 p.s.i. High cyclic stresses at high pressures have caused such pump heads to fail due to metal fatigue at a variety of locations within the fluid end. Typical fatigue points include: the packing-cartridge-fluid-cylinder interface; the recess for a front bushing; a recess within the fluid cylinder for the packing spring; recess for the suction valve spring; and a recess for a discharge valve flow.
U.S. Pat. No. 4,758,135 (co-owned with this invention) discloses another pump head having a fluid cylinder connected to a retainer plate which is connected to a pump manifold. The manifold has an inlet recess containing a suction valve. This inlet recess communicates with a fluid cylinder recess in which is disposed a plunger. A packing cartridge is threadedly connected to and disposed partially within an end of the fluid cylinder. The plunger moves in the fluid cylinder recess and within a recess in the packing cartridge. The suction valve inlet recess communicates with both the fluid cylinder recess containing the plunger and with a discharge recess which contains a discharge valve. The discharge recess is sized such that turbulence occurs therein inhibiting flow. Packing is disposed within the fluid cylinder recess and extends into the recess within the packing cartridge nut. The packing serves the purpose of sealing between the plunger and the packing cartridge. The packing cartridge has a large outer diameter. A packing spring is placed within the fluid cylinder recess for urging the packing in a direction away from the retainer plate for the purpose of maintaining load on the packing to effect a seal between the plunger and the packing cartridge. O-ring seals are employed at either end of the packing cartridge nut for insuring the sealed contact of the nut and the fluid cylinder. Front and rear bushings (or front and rear "brasses") are provided within the fluid cylinder recess and the packing cartridge nut recess about the plunger for aligning the plunger within the pump. A lube channel is provided from the exterior of the fluid cylinder, through the packing cartridge nut, to the rear bushing for the purpose of providing lubrication to the rear packing. A "pony rod extension" connects a power end to the pump plunger and permits removal of the plunger from the pump head without having to remove the pump head from the power end. Capscrews are used to hold the manifold, retainer plate, and fluid cylinder in sealing contact. The suction valve is spring loaded so that it will close quickly. On the suction stroke water moves from the suction manifold, past the suction valve, and into the fluid cylinder. On the discharge stroke, the suction valve closes stopping flow through the fluid cylinder back into the suction manifold. A high pressure seal is located at the interface between the fluid cylinder and the packing cartridge. By decreasing the diameter of the high pressure seal, the load on the packing nut threads is reduced (since load is directly proportional to the area, i.e., also to the diameter; thus, as the diameter is decreased while pressure is held constant, the load is decreased).
In both of the prior art pump heads described above, a retainer plate is used for housing a valve seating cartridge. Removal of the valve seat cartridge for maintenance can, at times, be difficult particularly if debris wedges the cartridge in the retainer plate. With neither of the above-described prior art fluid ends is high volume capacity available when operating over a range of pressures from relatively low to relatively high pressures, e.g. from 4000 to 15000 p.s.i. with a flow rate varying from 10 to 65 gallons per minute in a quintiplex configuration (five individual fluid cylinders each with a plunger in a fluid end of a pump.) With the prior art pump heads the discharge valve and channel is significantly smaller than the suction valve and channel, restricting flow capacity. None of the above-described pump heads permits more than five interchangeable plunger sizes. This further limits these prior art devices' range of volume capacity. None of the above-described prior art devices discloses valve return springs strong enough to withstand increased volume capacity and constant recycling over long periods.
There has long been a need for a fluid cylinder for a pump head with a wide range of flow rates and pressures which permit a wide size range of interchangeable plungers. There has long been a need for springs for a pump head that do not fail in pumping increased volumes over long periods of operation. There has long been a need for a fluid end in which the valves are easily accessible.
In accordance with 37 C.F.R. .sctn.1.56, the following are disclosed, incorporated fully herein by reference, and copies are submitted herewith.
U.S. Pat. No. 3,870,439 (discussed above).
U.S. Pat. No. 4,758,135 (discussed above).
"NLB Corp. Makes Water Work," National Liquid Blasting Corporation.
"NLB Corp. Model 10250 Quintuplex Plunger Pump," NLB Corp.
"Aqua-Dyne Value-In-Line, Modular Block, Fluid End Conversion Kits" Aqua-Dyne Incorporated.
Partek H & L - 300 Pumps By Butterworth," Butterworth Jetting Systems, Inc., 1987.
"Partek's `L` Design Fluid End," Butterworth Jetting Systems, Inc.
"The Weatherford Advantage," pp. 6-7, Weatherford Water Jetting Systems (1988).